Certified Rhythm Analysis Technician (CRAT) Practice Exam

In assessing a wide QRS complex that originates from above the ventricles, a bundle branch block is indeed a relevant consideration. A bundle branch block occurs when there is a delay in conduction through one of the bundle branches in the ventricles, resulting in a wide QRS complex on the electrocardiogram (ECG).

This is crucial because, while the dysrhythmia originates above the ventricles, the mechanism of conduction delay within the ventricle leads to the characteristic widening of the QRS complex. In bundle branch blocks, the QRS duration typically exceeds 120 milliseconds. This distinguishes it from other rhythms that may originate at or above the atrial level and typically present with narrow or normal QRS complexes.

Furthermore, in the context of the other options, supraventricular tachycardia usually features narrow QRS complexes, and while third-degree AV block may lead to a wide QRS in some cases (especially if there is an underlying bundle branch block), it typically has a more complex presentation with dissociation between atrial and ventricular activities. Atrial fibrillation, on the other hand, also presents with a narrow QRS complex unless accompanied by a bundle branch block.

Thus, identifying a wide QRS complex indicates